Parvovirus infection is responsible for erythema infectiosum (Fifth?s disease) in children and aplastic crisis, hemolytic anemias, and fetal death, as well as a rheumatic syndrome in adults. It is also reported to be responsible for anemias, fevers, pneumonitis, and aplastic crisis in AIDS patients. The human B19 parvovirus is most commonly implicated. Little is known about B19 due to its difficult in vitro propagation. Histologic evidence was shown in the bone marrow of a severely anemic rhesus monkey with advanced SIV immunodeficiency disease and suggested parvovirus infection in the rhesus as well. Bone marrow and other tissues from this animal were collected and cryopreserved. A pilot study was conducted to determine whether we could reisolate virus as well as reproduce the disease, and whether immunodeficient animal would more readily progress to disease, and if SIV is a cofactor of disease. We developed a molecular PCR assay for diagnosis of infection. Six animals were inoculated intravenously with the bone marrow preparation. 2of 3 naive animals not only developed progressive SIV immunodeficiency disease, but also severe anemia coincident with high reticulocytes and Parvovirus viremia the time of necropsy. The 3 previously SIV-infected animals, however, had only one animal progress to SIV disease, but none became anemic. A second study was then conducted with six additional SIV infected animals. Only two of six became infected and viremic. One animal progressed to disease, and Parvovirus was documented at necropsy, however, again no anemia was apparent. We are following the other animal for signs of SIV disease and/or anemia. This resistance to disease progression in the previously infected SIV animals was observed in both studies. It may be due to a lack of severe immunodeficiency from the original SIV. These animals were relatively stable, having all been infected with SIV for 1.5years or greater. In addition, they appear resistance to superinfection with the second SIV strain in the bone marrow inoculum, which had a more rapid disease course in the naive animals. FUNDING Base Grant, Venture Research. PUBLICATIONS None